What produces the myelin sheath in the PNS?

• A. Schwann cells
• B. Oligodendrocytes
• C. Astrocytes
• D. Microglia

Answer: (A)

Schwann cells are the glial cells of the peripheral nervous system responsible for forming the myelin sheath. Each Schwann cell wraps its membrane around a segment of a single axon, creating a multilayered myelin sheath and leaving gaps between segments called nodes of Ranvier. This insulation speeds electrical signaling through saltatory conduction. In contrast, in the central nervous system myelin is produced by oligodendrocytes, which can myelinate multiple axons with their processes. Astrocytes support neurons and help maintain the neural environment, while microglia act as immune cells in the CNS. Thus, myelin in the PNS is produced by Schwann cells.